From: Dave Hansen <dave.hansen@intel.com>
To: Dan Williams <dan.j.williams@intel.com>, Toshi Kani <toshi.kani@hpe.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Matthew Wilcox <willy@linux.intel.com>,
Ross Zwisler <ross.zwisler@linux.intel.com>,
mauricio.porto@hpe.com, Linux MM <linux-mm@kvack.org>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
"linux-nvdimm@lists.01.org" <linux-nvdimm@ml01.01.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping
Date: Wed, 2 Dec 2015 14:00:30 -0800 [thread overview]
Message-ID: <565F69FE.601@intel.com> (raw)
In-Reply-To: <CAPcyv4jtVkptiFhiFP=2KXvDXs=Tw17pF=249sLj2fw-0vgsEg@mail.gmail.com>
On 12/02/2015 12:54 PM, Dan Williams wrote:
> On Wed, Dec 2, 2015 at 1:37 PM, Toshi Kani <toshi.kani@hpe.com> wrote:
>> > On Wed, 2015-12-02 at 11:57 -0800, Dan Williams wrote:
> [..]
>>> >> The whole point of __get_user_page_fast() is to avoid the overhead of
>>> >> taking the mm semaphore to access the vma. _PAGE_SPECIAL simply tells
>>> >> __get_user_pages_fast that it needs to fallback to the
>>> >> __get_user_pages slow path.
>> >
>> > I see. Then, I think gup_huge_pmd() can simply return 0 when !pfn_valid(),
>> > instead of VM_BUG_ON.
> Is pfn_valid() a reliable check? It seems to be based on a max_pfn
> per node... what happens when pmem is located below that point. I
> haven't been able to convince myself that we won't get false
> positives, but maybe I'm missing something.
With sparsemem at least, it makes sure that you're looking at a valid
_section_. See the pfn_valid() at ~include/linux/mmzone.h:1222.
next prev parent reply other threads:[~2015-12-02 22:00 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-23 20:04 [PATCH] mm: Fix mmap MAP_POPULATE for DAX pmd mapping Toshi Kani
2015-11-23 20:53 ` Dan Williams
2015-11-23 22:15 ` Toshi Kani
2015-11-30 22:08 ` Dan Williams
2015-12-02 2:19 ` Toshi Kani
2015-12-02 3:45 ` Dan Williams
2015-12-02 17:43 ` Toshi Kani
2015-12-02 17:01 ` Dan Williams
2015-12-02 18:06 ` Dan Williams
2015-12-02 19:26 ` Toshi Kani
2015-12-02 19:00 ` Dan Williams
2015-12-02 20:02 ` Toshi Kani
2015-12-02 20:12 ` Toshi Kani
2015-12-02 19:57 ` Dan Williams
2015-12-02 21:37 ` Toshi Kani
2015-12-02 20:54 ` Dan Williams
2015-12-02 21:55 ` Toshi Kani
2015-12-03 23:43 ` Dan Williams
2015-12-04 16:55 ` Toshi Kani
2015-12-02 22:00 ` Dave Hansen [this message]
2015-12-02 22:03 ` Dan Williams
2015-12-02 22:09 ` Dave Hansen
2015-12-03 0:21 ` Toshi Kani
2015-12-02 23:33 ` Dan Williams
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